What it means
The signals of A/C refrigerant pressure sensors A and B do not correlate within the calibrated tolerance. One sensor drifts or installation offset between the two channels.
At a glance
- Usually lights the check-engine light
How it works
The A/C system uses refrigerant pressure sensors A and B to report pressure to the control module. This code sets when the two sensor readings disagree beyond the vehicle's calibrated tolerance, which can happen if a sensor has drifted or the channels are connected to the wrong harnesses.
Common causes
Most likely first.
- One sensor characteristic drifted
- Harness incorrectly swapped between channels
Symptoms
- Check-engine light
- Air conditioning may cool poorly or inconsistently
How to diagnose it
- Save freeze-frame data and read live pressure values from both A and B before clearing the code, noting whether the A/C was running.
- With the system off and conditions stable, compare the two readings and check whether they agree as expected under the manufacturer's diagnostic information.
- Visually trace the connectors and harness branches for sensors A and B to check for swapped plugs, damaged insulation, corrosion, or loose pins.
- Check each sensor's mounting and connector identity against the vehicle wiring information to confirm the A and B channels have not been interchanged.
- Test both sensor circuits and compare sensor output with a known pressure measurement using the vehicle's specified procedure to identify drift or wiring faults.
Common fixes
- Reconnect the A and B harnesses to their correct sensors if the channels were swapped.
- Clean and secure corroded or loose pressure-sensor connector terminals where repair is appropriate.
- Repair damaged wiring in the affected sensor branch.
- Replace the pressure sensor shown by testing to have drifted, then verify that A and B readings correlate.
Can I keep driving?
You can generally drive if the vehicle runs normally, but A/C cooling may be weak or inconsistent. Avoid relying on the system for defogging if it cannot clear the windscreen.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.